Tandem Cycling - Mushy rear brakes
Bikeforums.net is a forum about nothing but bikes. Our community can help you find information about hard-to-find and localized information like bicycle tours, specialties like where in your area to have your recumbent bike serviced, or what are the best bicycle tires and seats for the activities you use your bike for.
01-11-04, 08:28 PM
I’m still new to tandeming, my wife and I bought a new Trek T2000 a couple of months ago. I have never been happy with the Avid center pull brakes that came on the bike. I suppose my largest complaint has to do with the “mushy” feel of the rear brake. This complaint is of course in addition to an overall feeling that the bike has a total lack of braking power. My last posting on this forum was also related to my dissatisfaction with tandem brakes, as I was looking into disc brakes. However, at this time I’m not ready to spend the money experimenting with disc brake systems.
In the mean time, my ideas to help the mushy feel problem are to do the following:
Replace the brake cable housing with Odysey “compression-less” housing to eliminate housing compression. The Downhill mountain bikers use this cable on mechanical discs. The strands in this cable housing are not spiral wound, but are run linear like a shift cable. The housing is wrapped with Kevlar.
Eliminate cable stretch by sliding a length of brass tubing over the brake cable as it runs the length of the top tube. Silver soldering the ends of the tube to the cable. Although the cable has basically been bypassed with the "solid" tubing, it remains intact
I welcome your thoughts and comments.
01-11-04, 11:23 PM
FWIW: The Avid Shorty 6 which -- I believe -- is what came on your T2000, is actually one of the better brakes that you can put on a tandem fitted with bosses on the rear stays and front forks. When properly adjusted, Avid's Shorty 6 cantilever offers better braking and is far easier to adjust than the linear-pull brakes (aka. V-Brakes) and it is one of the brakes that many of us who make recommendations recommend folks switch to if they are unhappy with the V-brakes and travel agent.
The compressionless housing would probably improve the brake lever feel but, before spending the money for the upgrade, make sure that you've got the Shorty's adjusted properly, i.e., the blocks make full contact with both sides of the rim and with not more than 1-2mm of travel. You can also give your rim sidewalls a quick cleaning by pinching a strip of 3M's Scotch Brite between your brake blocks and the rim by applying a moderate amount of brake force and rotating the rear wheel through the brakes/Scotch Brite by hand for several revolutions.
You might also check to see how much your rear seat stay's are flexing when you apply your rear brakes -- works best if you use a helper to pull on your brake lever while you watch your stays from the rear of the bike. I've never checked this on the T2000, but it's not at all uncommon with cantilevers on tandems (our Cannondale MT3000 flexed a ton) and can be solved by fitting a "brake-booster" to your rear brakes. One of my favorite boosters is daVinci's "small stiffy".
My guess is, if properly adjusted -- and with the addition of the brake booster if you find that your rear stays are flexing -- you'll find you have no problems locking up the rear wheel.
Oh, the other brakes that are often times recommended are Tektro Mini-V's, Paul's Strange Brakes, and the no-longer produced Avid Arch Supremes which had a built-in brake booster. Perhaps the most powerful cantilever rim brake ever produced is Magura's HS-33 which, as you would expect, also had an integral brake booster. Unfortunately, the Magura's hydraulic rim brake could only be used with a non-intregrated drop-bar brake lever and bar-end shifter configuration. Someone (Edco?) made a few STI compatible hydraulic brake levers but they are VERY hard inf not impossible to find.
I had some trouble getting as much power as I thought I deserved out of the cantilever system on my pre-'98 Cannondale J/L, which I had parted together from a frameset (back then the Cannondale tandem was only available as a frameset) with hot-rod parts, i.e., Pedersen (sp?) self-energizing front brake, and the Suntour SE XC rear brake (Suntour refused to make a self-energizing front because they thought the injury rate would be too high).
I started out with true wheels and short pad travel, but while I could get the pads to the rims, I couldn't get them to bite as hard as I wanted.
The solution, of course, as you have guessed, is to remove mush and increase travel.
Starting from the front:
1. The cable housing cannot flex with brake application between where it comes out from under the handlebar tape and enters the cable housing stop on the top tube. You can stamp some of this out by zip-tying the front and rear brake cable housings together where they cross.
2. You have to have rigid cable housing stops. They can't flex under brake application. Apply the brakes and see if they flex. Replace them if they do. I got lucky and picked a forged Ritchey part that was really stiff the first time for the front brake cable housing stop, but when I tried to replace it with a more trick part, I discovered the new part was flexible junk. Back went the Ritchey. Did they call those "brake cable hangers", back then?
3. You have to have unkinked and unbent (straight!) cables. The little fellas will be bent until you apply the brakes, and then the kinks and bends will straighten out, stealing your travel that you would otherwise have used to bite on the rims.
4. Everything okay so far? Okay, here's the real secret that not many people know: it matters how you set up your straddle cable. If it's short and just clears the tire, you will have lots of leverage and not much movement. If it's as long as you can possibly safely set it, you will have not much leverage and lots of travel. The upper limit is that you can't run your straddle cable saddle (what's that thing called? can't remember?) into the cable housing hanger, or the first thing it runs into that it won't fit through...but you can set it just below that. Go back to the bike shop for new straddle cables that haven't had the ends cut off yet if you have to. Could be the bike shop guys didn't know much about cantilever brakes, and set them short and cut them off. Could have happened at the factory too. Get lots of travel and your brake pads will get to the rim quick and there will be travel left to bite with.
Anyways, after I was done I had more than enough bite, and I lived happily ever after with a bunch of stokers who still think I am safe.
Cable is actually high-technology stuff, and I am hesitant to heat it up, even only as little as to silver-solder. Anyway, you don't need to. A straight run of cable is inelastic enough to do the job. I think it wouldn't help, might fail, and anyway, your problem is elsewhere.
Write back and tell us how you are doing?
01-12-04, 05:22 PM
Following Mark’s advice above, I had my wife apply the rear brakes while I measured for flex in the stays. The result was that I could find no measurable amount of flex. Therefore the addition of a booster would not help.
O.k. so here is what I ended up doing. I bought and installed the Paul’s brakes for the front and rear. While installing the Paul’s Components, I went with the Odyssey “compression-less” housing. I also went ahead and installed the tube as a sleeve over the cable. Of interesting note was that after silver soldering the front of the sleeve, I hooked the brake system up and pulled hard on the cable, noting how much the cable moved in relation to the sleeve. The stainless steel cable stretched a little over ¼ of an inch! The difference in the feel once the other end of the cable was soldered was tremendous!! Testing the bike with just me on it I found that much of the mushy feel has been eliminated, now I’ll have to get my stoker on board for the real test.
01-12-04, 05:50 PM
Following Mark’s advice above, I had my wife apply the rear brakes while I measured for flex in the stays. The result was that I could find no measurable amount of flex.
That's a good thing...
I bought and installed the Paul’s brakes for the front and rear. While installing the Paul’s Components, I went with the Odyssey “compression-less” housing. I also went ahead and installed the tube as a sleeve over the cable. ... The difference in the feel once the other end of the cable was soldered was tremendous!!
Excellent. Perhaps there's an untapped market out there for solid rear tandem brake cable connecting rods! Just integrate with a pair of daVinci's cable splitters and viola, better performing rear brakes. The triplet and quad folks would REALLY benefit from such a device if you assume a proportional amount of cable stretch per linear foot of top tube.
01-12-04, 08:14 PM
The brakes you have (Avid Shorty 6, according to Mark Livingood) are good, but cantilever brakes are finnicky to adjust. That's the downside of offering many adjusting possibilities.
Another aspect that could help would be to replace your brake pads by Kool Stop Salmon. Compared to the default Shimano or Avid pads, they offer a bit better braking when it's dry, but much better when it's wet, and rim wear is less with Kool Stop than with Shimano or Avid pads.
01-12-04, 09:42 PM
The Avids were not that hard to adjust, they just took a bit of time to get “spot on”. The Paul’s I just bought actually came with Kool Stops! I have been using Paul’s Components brakes with Kool Stops on my mountain bike for several years, perhaps that’s one of the reasons I’ve been so critical of the brakes the T2000 came with, I was just used to a higher standard. That being said, I now think that perhaps a large portion of the “mushy” problem came from cable stretch and cable housing compression.
01-18-04, 10:23 PM
Howdy from Tucson!
Inherently tandem rear brakes do not feel as good as on a single bike due to the extra cable length.
If you have canti brakes here are possible improvements. Replace rear canti with a V-brake + add a force multiplier (like Avid TravelAgent) or a brake booster that basically attaches on to the canti-studs and stiffens up braking a bit. Also do not be afraid on a tandem to make more use of the front brake (shortest cable run) as you cannot do an endo on a tandem as you could on a single by really grabbing the front brake only. If you have the space and a threaded rear hub for a drum brake (usually operated by the stoker) that could be another solution especially for fully loaded downhill runs.
Hope this helps!
Pedal on TWOgether!
Rudy & Kay/Zona tandem
Powered by vBulletin® Version 4.1.12 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.